Preheat your oven to 350°F (175°C). In a mixing bowl, cream together softened cream cheese until smooth, then gradually mix in granulated sugar and flour until fully combined. Add vanilla extract, ground cinnamon, and heavy cream, mixing well. Add eggs one at a time, ensuring each is fully blended. Pour batter into a prepared 9-inch springform pan and bake for 10 minutes. Lower the oven temperature to 200°F (93°C) and bake for an additional 30-35 minutes until set. Cool and refrigerate overnight.

While the cheesecake cools, preheat the oven to 350°F (175°C). In another mixing bowl, cream butter and brown sugar until light and fluffy. Mix in vegetable oil, eggs, and vanilla extract until well-blended. In a separate bowl, sift together all-purpose flour, baking powder, and spices. Incorporate dry mixture into wet ingredients, then add milk to achieve a smooth batter. Pour into a greased 9-inch cake pan and bake for 15-17 minutes or until a toothpick comes out clean. Cool and refrigerate overnight.

In a bowl, whip unsalted butter until light and fluffy. Gradually add powdered sugar, mixing until blended. Add vanilla extract and heavy whipping cream, mixing until achieving a thick and spreadable consistency. Optionally sprinkle in ground cinnamon. Set aside for assembly.

Trim the edges of the cheesecake for even layers. Place cheesecake on a flat surface or cake stand. Spread a layer of buttercream frosting on top, then stack the spice cake, pressing gently. Add the store-bought pumpkin pie on top. Frost the entire assembled Piecaken with remaining buttercream, covering all sides. Refrigerate for a few hours or overnight to set perfectly.